The invention relates to a method of manufacturing a multilayer film consisting of a stack of primary soft-magnetic layers and secondary non-magnetic layers on a substrate by way of reactive sputtering.
Reactive sputtering is a technique which has been known for a long time, in which a target is bombarded with ions from a plasma which is generated by inserting a gas into a vacuum reactor vessel in which a substrate on which a layer must be provided is placed opposite the target, and by applying a high voltage which is negative with respect to the wall of the reactor vessel to the cathode formed by the target. The ions are thereby accelerated towards the target where cascade collisions are generated which result in an exiting of target material atoms located close to the surface. The direction of the particles thus sputtered with respect to the normal on the target surface is mainly cosine-distributed. It is common practice to use an inert gas such as Ar (or possibly, for example, Kr or Xe) in the reactor vessel, although also an active gas such as N.sub.2, O.sub.2 or CH.sub.4 and the like may be used or added to the inert gas, dependent on specific applications.
This sputter-deposition technique is used, inter alia, for manufacturing multilayer films for magnetic heads. The multilayer film consists of a stack of primary soft-magnetic layers and secondary non-magnetic layers on a substrate. Particularly, the primary soft-magnetic layers have a thickness of the order of 0.1 to 10 .mu.m and the secondary non-magnetic layers have a thickness of the order of 100 to 300 nm.
Examples of applying a soft-magnetic layer on a substrate by way of sputtering are given in, inter alia, U.S. Pat. No. 5,466,539. This patent states (in column 2, lines 64-67 and column 3, line 1) for example, a primary soft-magnetic layer which consists of an Fe.sub.x M.sub.y alloy, in which M is at least one element of the group comprising inter alia Nb, Zr, Hf, Ti, Ta, Si and x is an atom percentage of approximately 90% and y is an atom percentage of approximately 10%, which soft-magnetic layer is provided by means of a gas mixture consisting of Ar with approximately 3% of O.sub.2. The soft-magnetic layer mentioned in this U.S. patent has a thickness of 1.5 .mu.m and is provided by way of sputtering with the aid of a plasma obtained from said gas mixture on a SiO.sub.2 substrate which has a thickness of approximately 0.5 mm.
In the conventional manufacture of multilayer films for magnetic heads, sputtering techniques as described hereinbefore are used, in which the different composition of the primary soft-magnetic layer and the secondary non-magnetic layer is based on different targets. For example, it is known to use a CoZrNb target for the primary soft-magnetic layer and a ZrO.sub.2 target for the non-magnetic layer. Thus, two targets having a different composition are used every time.